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@PHDTHESIS{Frehn:952709,
author = {Frehn, Anica Renate},
othercontributors = {Monti, Antonello and Andresen, Björn},
title = {{U}nder voltage ride through tests on nacelle test benches
equipped with a power hardware in the loop setup; 1.
{A}uflage},
volume = {112},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {E.ON Energy Research Center, RWTH Aachen University},
reportid = {RWTH-2023-02183},
isbn = {978-3-948234-26-3},
series = {E.On Energy Research Center : ACS, Automation of Complex
Power Systems},
pages = {1 Online-Ressource : Illustrationen, Diagramme},
year = {2023},
note = {Druckausgabe: 2023. - Auch veröffentlicht auf dem
Publikationsserver der RWTH Aachen University; Dissertation,
RWTH Aachen University, 2022},
abstract = {Wind energy is the leading energy source in Germany and
therefore significant for a safe and reliable grid
operation. To ensure supply stability, proof of grid
compliance of the Wind Power Plant (WPP) is required. This
includes measuring the electrical characteristics and
creating and validating a Wind Turbine Generator System (WT)
model. IEC 61400-21-1 defines the testing requirements,
supplemented in Germany by FGW TG3, to demonstrate
compliance with grid connection rules. The measurement of
the electrical characteristics is currently performed on the
installed turbine in the field. Due to dependence on weather
and grid conditions, this approach can be very time
consuming and costly. In addition, individual measurements
are not reproducible due to fluctuating external conditions.
Nacelle test benches offer the possibility to measure the
electrical characteristics under laboratory conditions and
are suitable to replace the field measurement or parts of
it. Grid emulators, usually installed on test benches,
represent an artificial grid as a fully controllable voltage
source. They offer a variety of new setting options and
defined input parameters that are not available with the
previous test methods based on voltage dividers in the
field. Thus, even today’s commercially available grid
emulators offer test possibilities that go beyond the
requirements defined in the standards. As a further
component of the certification, grid emulators enable the
validation of the WT models under known, predefined input
parameters. This increases the accuracy of the model
validation by eliminating previous uncertainties, such as
the grid condition, which are not precisely known during
field measurements. At the same time, grid emulators have an
increased modelling effort as they are an actively
controlled system. However, detailed analyses of the
required model depth indicate that it is sufficient to embed
the impedance replication in the simulation. The main
scientific contribution of this work is to define the
necessary extensions of the technical guidelines to take
into account the extended setting possibilities that are
already provided by today’s grid emulators. The aim is to
maintain the high quality of the UVRT tests and the
comparability of the individual measurements. Some of the
proposed extensions have already been included in current
technical guidelines such as FGW TG3 Rev.26 and IEC
61400-21-4. In addition, this work identifies potential
additions to the existing test procedures as well as new
test possibilities. This is mainly done by experimental
investigations at the 4 MW test bench at Center for Wind
Power Drives (CWD), supplemented by individual simulations.
In addition to a freely adjustable voltage and frequency,
grid emulators enable the controllability of the grid
parameters at the connection point. This allows for the
first time the investigation of the UVRT behaviour at
different grid conditions. The WT behaves differently
depending on the set grid parameters, which not only affects
the reproducibility of the field measurement on the test
bench. Rather, it complicates the comparability of
individual UVRT measurements. The comparison of a test bench
measurement and a field measurement with an identical
turbine proves the reproducibility of the field measurement
on the test bench under the assumption of identical grid
parameters. A further test series shows that the
transferability of the results is not guaranteed in the case
of strongly deviating impedance values between the test
voltage divider based test method and the grid emulator. The
WT behaves differently depending on the test method used. In
addition to the impedance emulation, grid emulators allow a
controllable voltage transition during the voltage dip. To
ensure conclusions about the parameters to be set for the
instantaneous voltages, the previous description of the
voltage profile based on effective values is not
unambiguous. A variant using dq0 components developed and
recommended by the author accounts for the variability
during the voltage transients and thus allows a clearer
definition of the expected voltage profile. This further
ensures the comparability of individual tests. As renewable
energy sources become more significant, the requirements for
these energy sources themselves are changing. As experiments
demonstrate, a preferential active power injection can be
beneficial in fault case, in contrast to the current
requirements in the grid codes. It provides greater voltage
support in grids with high resistive loads and ensures
stable frequency in grids driven by renewable energy
sources. It is therefore advisable to test the capability of
active power injection in the future, even in the fault
condition. To this purpose, grid emulators provide a unique
test environment due to the impedance emulation. The
adjustable transient voltage transition additionally allows
tests with different envelopes during the fault occurrence.
This allows the WT’s response to near and far faults to be
investigated to ensure the correct response of the WT to
stabilize the disturbed power system. The results of this
work consequently demonstrate that test benches equipped
with grid emulators not only reproduce previous field
measurements. Rather, due to the adjustable input
parameters, new test procedures arise that reflect the
characteristics of a power grid increasingly based on
renewable energies.},
cin = {616310 / 080052},
ddc = {621.3},
cid = {$I:(DE-82)616310_20140620$ / $I:(DE-82)080052_20160101$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
doi = {10.18154/RWTH-2023-02183},
url = {https://publications.rwth-aachen.de/record/952709},
}
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